1. Field of the Invention
The present invention relates to a fixing card for use with high frequency to carry out the die sorter test relative to active and passive elements formed on a semiconductor substrate.
2. Description of the Related Art
The so-called probe card is used to test characteristics of active and passive elements formed on a semiconductor substrate and those of such circuit parts as resistances arranged on the substrate independently of the active and passive elements. The probe card comprises an insulating board and probes (or probe needles) attached to the insulating board. The probes are made of conductive metal such as tungsten, vanadium alloy and beryllium alloy. The number of the probes is determined to correspond to that of pads which are formed on the semiconductor substrate to correspond to the active and passive elements and the circuit parts.
The probe card is used in the characteristic test process, as shown in FIGS. 1A and 1B, to examine electric characteristics of the active elements and the like on the semiconductor substrate as follows. FIG. 1A is a plan showing the main portion of the probe card and FIG. 1B is a front view showing the probe card used. Reference numeral 1 represents a through-hole. An insulating board 2 provided with the through-hole 1 at the center thereof includes probes 3 which extend radially from the through-hole 1. The insulating board 2 further includes at the rim portion thereof connectors for connecting the probes 3 to an IC tester (not shown). The connectors are electrically connected to the probes 3.
A fixing ring 4 made of material such as aluminium, plastics and ceramics is attached to one side of the insulating board 2, enclosing the through-hole 1, as shown in FIG. 1B, at the time when the die sorter test is to be carried out. Using the probing process applied to the insulating board 2, the probes 3 are fixedly soldered to that side of the insulating board 2 to which the fixing ring 4 is attached. The probe 3 extend downward along the slope of the fixing ring 4 with their one ends fixed by a specific bonding layer 5 so that they may be tilted relative to the underside of the insulating board 2 at a certain angle. The bonding layer 5 preferably used has a heat shrinkage rate less than .+-.5 .mu.m to ensure accuracy in position of the probe 3 when the die sorter test is carried out under a high temperature between 90.degree. C. and 120.degree. C. This is because the tip of each probe 3 which is contacted with the pad is appropriately positioned. As apparent from Fig. 1C (which shows only the main portion of the fixing card), that portion of each probe 3 which is extended from the fixing ring (and which is called the beam length of the probe 3) is set 5.5.+-.0.5 mm long. This beam length of each probe 3 has a height of 500 .mu.m when measured from the lower end of the fixing ring 4 in the vertical direction, and each probe 3 has a height of 2500.+-.300 .mu.m or more when measured from the under-side of the insulating board 2 in the vertical direction. The die sorter measurement is carried out while keeping the probes 3 correctly contacted with pads 7 formed on an integrated circuit element 6, and the number of the probes 3 are set equal to that of the pads 7.
The integrated circuit elements have been made these days to have extremely high integration, function and speed, as seen in the case of D-RAMs. This makes it necessary to carry out the die sorter test at high speed and with high frequency.
As apparent from FIG. 1B, however, the probes 3 are radially arranged on the underside of the insulating board 2 so as to correctly contact their tips with the pads on the integrated circuit element. This is because the print pattern is shaped radial. The distance extending from the device under test (DUT) needed to apply the die sorter measurement to the integrated circuit element to the pads which serve as measuring terminals on the integrated circuit element is thus made long, thereby causing the high frequency measurement not to be smoothly carried out. No high frequency measurement can be applied to some kinds of the integrated circuit elements.